University of Rochester, Rochester, NYUniversity of Rochester, Rochester, NYUniversity of Rochester, North Chili, NYUniversity of Rochester School of Medicine, Rochester, NY

Background:

In patients with osteoarthritis, bony defects in small joints of the hand can occasionally be seen with conventional radiography (CR). Such a condition may be called erosive osteoarthritis (EOA). Swelling may occur, and the term "inflammatory osteoarthritis" is occasionally used. The degree of actual synovial proliferation remains unclear. It also remains unclear if bony defects of EOA are associated with synovial proliferation, similar to rheumatoid arthritis (RA).

Objectives:

To assess if synovial proliferation and synovial hyperemia can be detected sonographically in EOA.

Methods:

1091 US studies obtained over 16 months were reviewed. All US studies were performed by a rheumatologist certified in musculoskeletal US, with >15 years of US experience. Studies were performed using a Toshiba Xario US machine with an 18 MHz linear transducer with differential tissue harmonic imaging and high-sensitivity Doppler capability, and a SonoSite M-Turbo machine.

Patients with a CR diagnosis of EOA were identified. For the diagnosis of EOA, the radiologist's final assessment was counted.

US studies of joints in which EOA had been described by CR were assessed for the following:

1. Effusion, defined as a distension of the hyperechoic, fibrous joint capsule by anechoic synovial fluid; 2. Synovial proliferation, defined as hypo- to hyperechoic tissue within the joint cavity and emanating from the hyperechoic, fibrous capsule; 3. Synovial hyperemia, defined as a pulsatile Doppler signal within the joint capsule, associated with synovial tissue. Doppler signals were graded as follows: 0 = no signal; 1 = single vessel dots; 2 = confluent Doppler signals occupying less than half of the identified synovial tissue; 3 = confluent Doppler signals occupying more than half of the identified synovial tissue.

US studies of 13 RA patients were randomly selected and scored as a comparison group.

Results:

Effusions were seen in 4/21 (19%) joints in EOA and 67/208 (32%) joints in RA. When effusions in EOA patients were seen, they were seen over the volar aspects of DIP and PIP joints, or immediately adjacent to bone spurs, where the spurs mechanically distended the joint capsule. Synovial proliferation was seen in 2/21 (9.5%) joints in EOA and 120/208 (58%) in RA. The degree was minimal in all cases of EOA. Only a concentric proliferation of the synovial lining was seen, but no invading pannus tissue was appreciated in EOA. Doppler scoring was 0 in 19/21 (90.5%) or 1 in 2/21 (9.5%) in EOA and 3 in 28/208 (13.5%), 2 in 52/208 (25%), 1 in 30/208 (14%) and 0 in 98/208 (47%) in RA.

Conclusion:

In this US study, synovial changes were found to be fundamentally different in EOA and RA. Increases in synovial fluid around bone spurs in EOA did not have an inflammatory character. Synovial proliferation in EOA was, in stark contrast to RA, minimal. Similarly, synovial hyperemia was rarely seen in EOA, while this is common feature of RA. Invading synovial tissue was not seen adjacent to bony defects in EOA. Using sensitive US technology, synovial proliferation and hyperemia were not characteristic of EOA.